Stupid question about CRT swaps??

[TV Engineer]

when I was in High School, I was given a Magnavox 21" round color theatre with a U45 chassis in it. I liked the set, and of course the stereo, but I didn't like that "big, old fashioned" round screen staring at me in my bedroom (it was a low end theatre, and did not have doors on it.) Besides, the corners were cut off on a round CRT, and I wanted to see the whole picture.

I worked at a Magnavox service center, so there were lots of old sets around that were scrapped, and the chassis and other usable parts thrown into the cellar for future use.

I had a 23VAQP22 CRT that had been salvaged from and Admiral color set, and I wondered if I could adapt this tube to my Mag theatre. The answer was yes, and it was actually easy.

From the cellar of the shop, I scared up a mask for a set that used a 25AP22 with all of the hardware and the shield, a yoke, and a convergence board. These probably came from a set that used the U904 or U911 chassis, as they were the first 2 that Magnavox made that used the rectangular CRT. Since Magnavox was pretty consistant with hardware patterns, the new mask replaced the old without having to drill a single hole. I rewired the yoke to match the 4 wire configuration of the old 21" round yoke, and using a schematic from each chassis, was able to match the wiring to the convergence board 1 for 1. Then, of course, I replaced the CRT socket.

The results were amazing.

The set performed as if it were designed to use the 23" CRT, with absolutely no convergence, width, or pincushion problems whatsoever. I realize that most of this was dumb luck now.

I would NEVER do it again. I've learned to like that "old fashioned" CRT staring at me!